Medical Oncologists use drug therapy such as chemotherapy, immunotherapy or biologic therapies to treat cancerous cells. Drug therapy has been used for many years and is one of the most common treatments for cancer. In most cases, drug therapy works by interfering with the cancer cell’s ability to grow or reproduce. Different groups of drugs work in different ways to fight cancer cells. Drug therapy may be used alone for some types of cancer or in combination with other treatments such as radiation or surgery. Often, a combination of drug therapy drugs is used to fight a specific cancer. Certain drug therapy drugs may be given in a specific order depending on the type of cancer it is being used to treat.